(function() {
  var counter = 0;
  var numbered;
  var source = document.getElementsByClassName("prettyprint source");

  if (source && source[0]) {
    source = source[0].getElementsByTagName("code")[0];

    numbered = source.innerHTML.split("\n");
    numbered = numbered.map(function(item) {
      counter++;
      return '<span id="line' + counter + '" class="line"></span>' + item;
    });

    source.innerHTML = numbered.join("\n");
  }
})();
